Field Of The Invention
The present invention relates generally to computer systems, and more particularly, to a subsystem that provides for removal and replacement of core I/O devices while the rest of the computer system is powered-up and operational.
Statement of the Problem
Many computer products supply a minimal set of built-in I/O devices, often called xe2x80x98core I/Oxe2x80x99. These core I/O devices include I/O controllers for peripheral devices, bus management, and the like. In low-end systems these devices are located on the main system board. In high-end systems the core I/O devices are often located on a separate board that cannot be removed unless the system is shut down, i.e., the core I/O cannot be xe2x80x98hot-swappedxe2x80x99. Therefore, system downtime is incurred when a core I/O device is replaced in the case of a hardware failure or upgrade. Previously existing methods for providing core I/O generally fall into three categories:
(a) Core I/O functionality is built into the system (main) board;
(b) Core I/O is built into a card, separate from the main board, that is not hot-swappable, i.e., that cannot be replaced without shutting down (and thus rendering inoperable) the entire system; or
(c) Core I/O is built into a card compatible with a PCI (Peripheral Computer Interface) slot.
In the case of (a), above, where the core I/O is built into the main board, the system must be shut down and the system board removed in order to replace or modify the particular I/O devices of interest. This configuration can be costly when only I/O hardware needs to be replaced or upgraded.
When core I/O is located on a separate card that is not hot-swappable, as in (b), above, the I/O device(s) of interest can be replaced or upgraded without replacing the rest of the system board(s). However, the system must be brought down completely, thus decreasing system uptime and availability.
If core I/O is built into a PCI slot-compatible card, advantage can be taken of PCI""s specified hot-plug capabilities as described in the PCI specification, but connectivity to the rest of the system is severely constrained by card size and pin limitations. Furthermore, existing PCI cards accommodate only one device per card, which further limits the functionality of a core I/O card.
For higher-end computer systems, shutting down the system for maintenance is very costly, which is why emphasis is put on system xe2x80x98up-timexe2x80x99 and xe2x80x98high-availabilityxe2x80x99. What is needed is a system that allows for core I/O removal, addition, and replacement while the system remains operational. In addition, there is a need for flexibility in designing the core I/O card interface to the rest of the system.
3. Solution to the Problem
The present system solves the above problems and achieves an advance on the field by providing a mechanism for removing and installing I/O core hardware while a computer system is operating. Costly downtime usually associated with the replacement of I/O hardware is thus eliminated. Expansion of a system""s capabilities is thus greatly facilitated. For example, if a computer system has one or more available (unused) core I/O slots, additional I/O hardware can be added without incurring additional system down-time. In addition, existing hardware can be upgraded, or failed hardware can be replaced without incurring any additional system down-time.
The system comprises a custom form-factor core I/O card that contains a plurality of I/O devices, including a processor for managing the card""s I/O functions. In addition, the present system allows a core I/O board to have any desired type of interface to the computer system, including a common form such as a PCI slot, or alternatively, a completely custom interface. A custom interface is often necessary when the core I/O contains other functionality such as system management functions that require a unique set of signals to be transmitted between the I/O card and the computer system. Furthermore, the present system does not require that the power to the card slot be turned off when the card is inserted or removed.
In operation, a command is sent to an operating system (OS), running on a system processor, that notifies the system to stop using, and de-configure, the hardware on the core I/O card. This command can be initiated by a pushbutton, a software routine, or by some other method. Once the OS receives this notification, it quiesces the drivers, halts bus traffic, and may power down the slot. Then an indication that the card is ready to be removed is sent to the user. This indication may be provided by an LED, a software alert, or by some other mechanism.
The user then removes the card from its slot and inserts a replacement card into the same slot. Current limiters on the system side prevent spikes on the supply voltage rails from occurring when a card is first inserted into a slot and powered up. Once the card is powered up (if previously powered down), the system software can query the I/O components on the core I/O card to determine what components are available, and then configure the new I/O device(s).
The system core I/O may thus be switched without consuming costly downtime. The method of the present system is especially useful in systems having multiple core I/O boards and multiple OS instances or partitions. In systems having multiple partitions (or operating systems), an I/O board in one partition may be replaced while the remaining partitions (or operating systems) remain operational. In addition, the present system allows the core I/O card to be located either in an existing I/O slot such as a standard PCI slot, or in a custom slot specifically designed for a particular core I/O board. Using a custom slot allows greater flexibility in both system interconnect and in the mechanical design thereof.